This invention relates to a method for forming a moisture-permeable waterproof coating on fabrics.
Many different methods have been proposed for forming a moisture-permeable waterproof coating on fabrics. Most of known methods may be classified as a "wet coagulation process" in which a solution of a film-forming polymer in a water-miscible solvent is applied on a fabric followed by immersing the fabric in a water bath to coagulate the polymer into a microporous coating layer. Other known methods include the so-called "dry coagulation process" which utilizes a coating composition containing a blowing agent which generates a gas such as N.sub.2 or CO.sub.2 upon heating, or a pore-forming agent which may be leached out with water. Another known method comprises the steps of providing an aqueous emulsion of a film-forming elastomer, vigorously whipping the emulsion, applying the resulting whipped emulsion on a fabric and then drying.
All of these known methods, however, suffer from a common disadvantage that the pore size of the resulting water-proof coating layer varies to a great extent and thus it is difficult to control the pore size within a relatively uniform distribution range at which both waterproofness and moisture-permeability are compatible. Furthermore, the solvent-based dry coagulation process requires a large investment in systems for solvent recovery and the like.
It is therefore an object of this invention to provide an improved method for forming a moisture-permeable water-proof coating on a fabric which is free from the above-mentioned disadvantages. More particularly, the invention provides an improved method for manufacturing a moisture-permeable waterproof fabric with improved feeling and increased resistance to laundering and dry cleaning using a water-based waterproofing coating composition.